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We have examined within a fully self-consistent theoretical framework the energy difference between the anti-analog giant dipole resonance (AGDR) and the isobaric analog state (IAS), ${E}_{\mathrm{AGDR}}\ensuremath{-}{E}_{\mathrm{IAS}}$, as an indicator of the neutron skin and of the density behavior of the symmetry energy. We have improved two specific points in our HF+RPA calculations: (1) the exchange term of the two-body Coulomb interaction is treated exactly without Slater approximation; and (2) the two-parameters spin-orbit interaction is treated in a consistent way within the energy density functional theory. The estimated values for the neutron skin in $^{208}\mathrm{Pb}$ and the slope parameter of symmetry energy are compared with previous analysis available in the literature.

The influence of the core polarization on the effective nuclear interaction of asymmetric nuclear matter is calculated in the framework of the induced interaction theory. The strong isospin dependence of the density and spin density fluctuations is studied along with the interplay between the neutron and proton core polarizations. Moving from symmetric nuclear matter to pure neutron matter the crossover of the induced interaction from attractive to repulsive in the spin singlet state is determined as a function of the isospin imbalance.The density range in which it occurs is also determined. For the spin triplet state the induced interaction turns out to be always repulsive. The implications of the results for the neutron star superfluid phases are shortly discussed., Comment: 6 pages, 4 figures

A Skyrme-like effective interaction is built up from the equation of state of nuclear matter. The latter is calculated in the framework of the Brueckner-Hartree-Fock approximation with two and three body forces. A complete Skyrme parametrization requires a fit of the neutron and proton effective masses and also the Landau parameters. The new parametrization is probed on the properties of a set of closed-shell and closed-subshell nuclei, including binding energies and charge radii., 7 pages, 9 postscript figures

Effects of medium polarization are studied for $^1S_0$ pairing in neutron and nuclear matter. The screening potential is calculated in the RPA limit, suitably renormalized to cure the low density mechanical instability of nuclear matter. The selfenergy corrections are consistently included resulting in a strong depletion of the Fermi surface. All medium effects are calculated based on the Brueckner theory. The $^1S_0$ gap is determined from the generalized gap equation. The selfenergy corrections always lead to a quenching of the gap, which is enhanced by the screening effect of the pairing potential in neutron matter, whereas it is almost completely compensated by the antiscreening effect in nuclear matter., 8 pages, 6 Postscript figures

The isospin splitting of the nucleon mean field is derived from the Brueckner theory extended to asymmetric nuclear matter. The Argonne V18 has been adopted as bare interaction in combination with a microscopic three body force. The isospin splitting of the effective mass is determined from the Brueckner-Hartree-Fock self-energy: It is linear acording to the Lane ansatz and such that $m^*_n > m^*_p$ for neutron-rich matter. The symmetry potential is also determined and a comparison is made with the predictions of the Dirac-Brueckner approach and the phenomenological interactions. The theoretical predictions are also compared with the empirical parametrizations of neutron and proton optical-model potentials based on the experimental nucleon-nucleus scattering and the phenomenological ones adopted in transport-model simulations of heavy-ion collisions. The direct contribution of the rearrangement term due to three-body forces to the single particle potential and symmetry potential is discussed., 8 pages, 10 figures

The interaction between the mitotic spindle and the cellular cortex is thought to play a critical role in stimulating cell cleavage. However, little is understood about the nature of such interactions, particularly in tissue culture cells. We have investigated the role of the spindle midzone in signaling cytokinesis by creating a barrier in cultured epithelial cells with a blunted needle, to block signals that may emanate from this region. When the barrier was created during metaphase or early anaphase, cleavage took place only on the sides of the cortex facing the mitotic spindle. Microtubules on the cleaving side showed organization typical of that in normal dividing cells. On the noncleaving side, most microtubules passed from one side of the equator into the other without any apparent organization, and actin filaments failed to organize in the equatorial region. When the barrier was created after the first minute of anaphase, cells showed successful cytokinesis, with normal organization of microtubules and actin filaments on both sides of the barrier. Our study suggests that transient signals from the midzone of early anaphase spindles are required for equatorial contraction in cultured cells and that such signaling may involve the organization of microtubules near the equator.